[libc] wmemcpy implementation (#142070)

Implemented wmemcpy and tests for the function.

---------

Co-authored-by: Sriya Pratipati <sriyap@google.com>

libc/config/linux/x86_64/entrypoints.txt

@@ -369,6 +369,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wcspbrk
     libc.src.wchar.wcsspn
     libc.src.wchar.wmemcmp
+    libc.src.wchar.wmemcpy
 
     # sys/uio.h entrypoints
     libc.src.sys.uio.writev

libc/include/wchar.yaml

@@ -64,3 +64,11 @@ functions:
       - type: const wchar_t *
       - type: const wchar_t *
       - type: size_t
+  - name: wmemcpy
+    standards:
+      - stdc
+    return_type: wchar_t *
+    arguments: 
+      - type: __restricted wchar_t *
+      - type: const __ restricted wchar_t *
+      - type: size_t

libc/src/wchar/CMakeLists.txt

@@ -91,3 +91,15 @@ add_entrypoint_object(
     libc.hdr.wchar_macros
     libc.src.__support.wctype_utils
 )
+
+add_entrypoint_object(
+  wmemcpy
+  SRCS
+    wmemcpy.cpp
+  HDRS
+    wmemcpy.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+    libc.src.__support.wctype_utils
+)

libc/src/wchar/wmemcpy.cpp

@@ -0,0 +1,26 @@
+//===-- Implementation of wmemcpy -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/wchar/wmemcpy.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/string/memory_utils/inline_memcpy.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t *, wmemcpy,
+                   (wchar_t *__restrict s1, const wchar_t *__restrict s2,
+                    size_t n)) {
+  inline_memcpy(s1, s2, n * sizeof(wchar_t));
+  return s1;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wmemcpy.h

@@ -0,0 +1,23 @@
+//===-- Implementation header for wmemcpy ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WMEMCPY_H
+#define LLVM_LIBC_SRC_WCHAR_WMEMCPY_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+wchar_t *wmemcpy(wchar_t *__restrict s1, const wchar_t *__restrict s2,
+                 size_t n);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WMEMCPY_H

libc/test/src/wchar/CMakeLists.txt

@@ -84,3 +84,13 @@ add_libc_test(
   DEPENDS
     libc.src.wchar.wmemcmp
 )
+
+add_libc_test(
+  wmemcpy_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wmemcpy_test.cpp
+  DEPENDS
+    libc.src.wchar.wmemcpy
+)

libc/test/src/wchar/wmemcpy_test.cpp

@@ -0,0 +1,61 @@
+//===-- Unittests for wmemcpy ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/wchar/wmemcpy.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWMemcpyTest, CopyIntoEmpty) {
+  wchar_t dest[10] = {};
+  const wchar_t *src = L"abcde";
+  LIBC_NAMESPACE::wmemcpy(dest, src, 6);
+  ASSERT_TRUE(src[0] == dest[0]);
+  ASSERT_TRUE(src[1] == dest[1]);
+  ASSERT_TRUE(src[2] == dest[2]);
+  ASSERT_TRUE(src[3] == dest[3]);
+  ASSERT_TRUE(src[4] == dest[4]);
+  ASSERT_TRUE(src[5] == dest[5]);
+}
+
+TEST(LlvmLibcWMemcpyTest, CopyFullString) {
+  // After copying, strings should be the same.
+  wchar_t dest[10] = {};
+  const wchar_t *src = L"abcde";
+  LIBC_NAMESPACE::wmemcpy(dest, src, 6);
+  ASSERT_TRUE(src[0] == dest[0]);
+  ASSERT_TRUE(src[1] == dest[1]);
+  ASSERT_TRUE(src[2] == dest[2]);
+  ASSERT_TRUE(src[3] == dest[3]);
+  ASSERT_TRUE(src[4] == dest[4]);
+  ASSERT_TRUE(src[5] == dest[5]);
+}
+
+TEST(LlvmLibcWMemcpyTest, CopyPartialString) {
+  // After copying, only first two characters should be the same.
+  wchar_t dest[10] = {};
+  const wchar_t *src = L"abcde";
+  LIBC_NAMESPACE::wmemcpy(dest, src, 2);
+  ASSERT_TRUE(src[0] == dest[0]);
+  ASSERT_TRUE(src[1] == dest[1]);
+  ASSERT_TRUE(src[2] != dest[2]);
+  ASSERT_TRUE(src[3] != dest[3]);
+  ASSERT_TRUE(src[4] != dest[4]);
+}
+
+TEST(LlvmLibcWMemcpyTest, CopyZeroCharacters) {
+  // Copying 0 characters should not change the string
+  wchar_t dest[10] = {L'1', L'2', L'3', L'4', L'5', L'\0'};
+  const wchar_t *src = L"abcde";
+  LIBC_NAMESPACE::wmemcpy(dest, src, 0);
+  ASSERT_TRUE(L'1' == dest[0]);
+  ASSERT_TRUE(L'2' == dest[1]);
+  ASSERT_TRUE(L'3' == dest[2]);
+  ASSERT_TRUE(L'4' == dest[3]);
+  ASSERT_TRUE(L'5' == dest[4]);
+}